Many types of child-resistant closures are known in the prior art. In general, such closures require some purposeful manipulation, which is beyond the ability of a child, before the closure may be removed from the container. Two piece child-resistant closures are common. Typically, these include a threaded closure surrounded by an outer shell. The shell rotates freely relative to the threaded inner closure unless it is manipulated in a particular manner.
However, in many applications, for the sake of economy and simplicity, a one piece child-resistant closure is desired. A one piece child-resistant closure must operate in combination with a container having a specially designed neck or finish. In general, such combination have at least a pair of interlocking members, one on the closure and one on the container. When the interlocking members are interengaged, rotation of the closure relative to the container is prevented. At least one of the interlocking members is flexible, thereby permitting the interlocking members to be manually disengaged.
The following United States Patents are representive of prior art one piece child-resistant closures:
______________________________________ 3830391 Uhlig 3877597 Montgomery et al. 3894647 Montgomery 4103797 Morris ______________________________________
All of the above closures have undesirable features which adversely affect the reliability, the cost, or the versatility of the closure design.
The Uhlig patent discloses several embodiments, the most relevant of which are illustrated in FIGS. 1 through 7. The Uhlig closure has an upwardly deflectable tab on the closure engagable with a projection formed on the container neck. To assure the necessary flexibility, the tab is integrally formed on the periphery of a radially extending flange at the bottom of the closure skirt. Such a design requires a relatively large amount of material to form the flange, and requires a relatively large cooperating shoulder on the container neck.
The patents to Montgomery et al. disclose closures having a locking tab radially projecting from the bottom edge of the skirt. The tab is upwardly deflectable by manipulation. The skirt of the closure is also relatively flexible, to permit an upward deflection of the tab without undue stress at its juncture with the skirt.
The Patent to Morris discloses a container neck having a pawl mounted on a beam. The beam is axially deflectable and is integrally attached to the container wall by thin, flexible radial bars. These bars are relatively weak points in the structure of the child-resistant container.
An improved one piece child-resistant closure would reduce the amount of material necessary to manufacture the closure, would have a reliable yet flexible integral attachment of a locking member to the closure skirt, would minimize the necessary diameter of th closure skirt, and would permit greater latitude in container shoulder design.